Targeted Therapy for — Neuroendocrine Tumours

PRRT stands for peptide receptor radionuclide therapy. A radioactive substance is attached to a molecule that binds specifically to somatostatin receptors on your tumour cells. It delivers radiation from inside the tumour rather than from an external beam, which means surrounding healthy tissue receives far less exposure. PRRT is considered for receptor-positive NETs that have progressed despite somatostatin analogues, and it is given at specialist nuclear medicine centres rather than every oncology unit. NCCN and ESMO include it in their guidelines for eligible patients.

The mTOR pathway controls how cells grow and divide. In certain NETs it is overactive, and mTOR inhibitors aim to slow that activity. The result is usually not a visible shrinking of the tumour but a slowing of growth — what oncologists call disease stabilisation. ESMO and NCCN evidence supports use of this class of drug in progressive, well-differentiated NETs of pancreatic, gastrointestinal, and lung origin. It is taken as a daily oral tablet and requires regular monitoring of blood sugar and kidney function during treatment.

A receptor-negative result on DOTATATE PET-CT means somatostatin analogues are unlikely to help and PRRT is not appropriate. It does not mean you are out of options. mTOR inhibitors and, for pancreatic NETs, VEGFR inhibitors remain available regardless of receptor status. For high-grade disease, cytotoxic chemotherapy may be recommended. Your oncologist will explain which path the evidence supports for your specific tumour grade and primary site.

Yes. A VEGFR-targeting agent is recommended by NCCN and ESMO as an option for progressive, well-differentiated pancreatic NETs, and it is not available for NETs arising in other sites. This is one reason pathology confirmation of your primary site matters early. Pancreatic NETs are also the subtype where DAXX and ATRX mutation testing is sometimes done, though those results carry prognostic rather than treatment-selecting weight in current practice.

Somatostatin analogues and mTOR inhibitors are generally continued for as long as the disease remains stable and you are tolerating the treatment. NETs are often slow-growing, so treatment is measured in months to years rather than the fixed cycles used in some other cancers. Response is monitored with regular scans and Chromogranin A checks. PRRT is given as a defined number of treatment cycles rather than continuously. Your oncologist will set out the monitoring schedule before treatment begins, so you know when each review is and what it is looking for.

For well-differentiated, low-grade NETs, chemotherapy is generally not the first choice and may not be needed at all. It is more commonly used in poorly-differentiated, high-grade neuroendocrine carcinomas, where the behaviour is more aggressive and the evidence supports a different treatment approach. The two disease types have meaningfully different treatment pathways, and your Ki-67 result is the key finding that separates them. Ask your oncologist which category your tumour falls into if the report is unclear.